This study will look at the ways in which Tylenol interacts with the sedative midazolam. Enzymes found in the liver and intestines degrade drugs that are taken orally. The effects of oral midazolam vary; some patients become sedated quicker and/or deeper than others, depending on the patients ability to degrade the drug. The same enzymes process Tylenol. We will use a unique cellular model and a clinical study to see if Tylenol modulates this enzyme and thereby increases the availability of oral midazolam. Moduation of enzyme activity may have important clinical and economic impact of many drugs, including the HIV protease inhibitors.